package JD;

import java.text.DecimalFormat;
import java.util.Scanner;

/**
 * Created by rzd on 2017/4/7.
 */
public class Main {
    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);

            int n=in.nextInt();
            int[] pi=new int[n];
            double[] Pi=new double[n];
        for (int i = 0; i < n; i++) {
            pi[i]=in.nextInt();
        }
        for (int i = 0; i < n; i++) {
            Pi[i]=pi[i]/100.0;
        }
        double tmp=n*0.6;
        int m= (int) tmp;
        if(tmp!=m)m++;
        double sum=0;
        for (int i = m; i <= n; i++) {
            sum+=compute(Pi,0,i);
        }
        DecimalFormat df=new DecimalFormat("#0.00000");
        System.out.println(df.format(sum));
    }

    static double compute(double[] pi,int i,int m)
    {
        int limit=pi.length-m;
        double tmp=1;
        if(i==limit){
            for (int j = i; j < pi.length; j++) {
                tmp=tmp*pi[j];
            }
            return tmp;
        }
        if(m==0)
        {
            for (int j = i; j < pi.length; j++) {
                tmp=tmp*(1-pi[j]);
            }
            return tmp;
        }
        return (1-pi[i])*compute(pi,i+1,m)+pi[i]*compute(pi,i+1,m-1);
    }

}
